DanubeBCL wrote:If you have room for a 300 m Beverage don't hesitate. Build it! Of course it is highly directional.
I do not have room for a Beverage, but my lousy 25 m "random" wire already outperforms both my 5 m and even my 14 m magnetic loop. But not in all directions, of course. The loops are better where the wire pattern has its "nulls". And the wire of course performs bad on VLF and LW. Here the loops a better.
If possible, use them both: Beverage for preferred DXing direction and Wellbrook for all directions.
If it had room for a Beverage, I would not hesitate ...
Heinrich makes several good points. back in the 1990s I read all the available information from Bell Labs on Beverage's original work, and have since designed and constructed many Beverages and BOG (Beverage on Ground) antennas for myself and for other hams and SWLs. There are some things you should keep in mind to get the "best" performance from you Beverage antenna -
The beverage antenna develops it's maximum gain when it is between 2 and 3 wavelengths long (depending upon wire height and ground conductivity under the antenna), but the Beverage will have it's sharpest directional selectivity when longer - typically 4 to 6 wavelengths. There is absolutely nothing wrong with having a "jumper" which can disconnect the last 1/4 to 1/3 of the antenna (away from the feedpoint) in order to choose for best directionality vs. best gain - but of course, then you will have to have a proper ground at the selected interim point, and provide a terminating resistor at the interim point as well providing these at the extreme end. Obviously, this gets a lot more complicated with a "reversible" Beverage setup.
The "shorter" beverages of 2 to 3 wavelengths generally don't require a receive pre-amp at their feedpoint when the matching transformer is well made, but it's not uncommon for the longer, "sharper" ones to require a pre-amp in order to obtain best performance in actual use.
Also important to remember is that even though a terminated Beverage is not a "resonant" antenna, it **is** Periodic - meaning that it's gain varies between maxima and minima following a periodic cycle - when the antenna is an odd multiple of quarter wavelengths long - 3/4, 5/4, 7/4, etc. - it has lowest gain; and when it is an even multiple of quarter wavelengths long - 6/4, 8/4, 10/4, etc. - it develops the highest gain.
With "average" soil types and an antenna height of 7~12 feet above ground, the variation in gain may be as little as 2 to 4dB (essentially unnoticeable except under the most marginal circumstances), but with particularly poor soil (solid rock, dry sand, etc.) the periodic variations may be as much as 8 or 10dB, and <b>will be most pronounced near the lower frequency bound of the antenna's directionality.</b>
Fortunately, both of these potential issues can be addressed effectively with a quality pre-amp at the antenna's feedpoint.
So how do I define "quality" with regards to the pre-amp?
1 - It must have a high IP3 (Most Important) ,
2 - it should implement some form of gain-limiting so as to smooth out the variations in signal level at the input - typically this is implemented by powering the amplifier from a controlled-current source, and taking the output as a "Cathode Follower" (a "Drain Follower" in MOSFET terms) across a fixed resistance which matches the impedance of your coaxial line - here's a page on using a tube as a Cathode Follower which will help you get the basic idea - https://www.ampbooks.com/mobile/amplifi ... -follower/
And 3rd, with an unterminated (Bi-Directional) Beverage you want to stabilize the input impedance seen by the amplifier- so it's best to have a resistor directly between the input terminal of the preamp and the signal ground, so that any reactance at the feedpoint of the antenna is swamped by the resistor; otherwise the reactance may ruin the [Beverage + pre-amp's] performance in certain portions of the spectrum, or even degrade the amplifier's stability, resulting in "birdies" (self oscillation) at one or more frequencies. This resistance (and the ratio of the matching transformer) will be determined by the designed input impedance of the preamp, and most likely will not match either the coax impedance or the "antenna impedance" (i.e. it will not be the same as the terminating resistor of a terminated Beverage).
OK, I've said a lot here - feel free to come back with more specific questions.